Fig. 1. Localization of endogenous ORP3 in HEK293 cells. Immunofluorescence microscopy analysis of HEK293 cells using anti-ORP3 antibodies. F-actin was stained with OG488P. The arrows in A and D indicate ORP3 staining at the filopodial plasma membrane extensions. The low-magnification views (G-I) visualize the loss of ORP3-positive filopodia in cultures of increased cell density. Specificity of the staining pattern is demonstrated by preincubation of the ORP3 antibody with the immunizing peptide, leading to loss of the immunoreactivity (J-L). Scale bars: 20 µm.